Look for a clan in the game modes you play that has numbers and seems to play pretty well in-game. That's the best way to find a clan to join. Asking here you won't get many responses since the clan forum is no longer active and what responses you do get will likely be from ones that rarely have numbers on or they're filled with nothing but a bunch of scrubs that try to snipe.
If you play Sabo a lot or bought the Escalation DLC look for clans like TR and U-W which have numbers and are active.
Message Quagers13. He has a really good Valor clan that's actively recruiting right now.